In a conventional connector described in JP 2003-343785A, a cylindrical connection member, in which a fluid flows, is inserted into a cylindrical insertion hole provided in a connector. Furthermore, an O-ring is inserted between the connector and the connection member so as to secure sealing performance therebetween.
In the connector described in JP 2003-343785A, a protrusion portion provided on an outer peripheral surface of the connection member is engaged with a recess portion provided on an inner peripheral surface of an insertion hole of the connector, thereby preventing the connection member from being removed from the connector. The recess portion of the connector is arranged at an inlet side of the insertion hole from an arrangement position where the O-ring is arranged. Thus, the O-ring passes the recess portion of the connector when being inserted into the insertion hole of the connector. Accordingly, while the O-ring passes the recess portion, the O-ring may be scratched by the recess portion, and may be damaged.
On the other hand, the home page of NOK corporation, searched on Mar. 1, 2009 from the Internet online (URL:http://www.nok.co.jp/seihin/O-rings pdf/bij.pdf), is described regarding an O-ring technical note. The O-ring technical note describes that, it is prefer to chamfer a hole portion in order to prevent a damage of an O-ring, if the O-ring is required to pass the hole portion when a connection member is connected to a connector.